Using a large, nationally representative sample of high school students in the US, we found that the patterns of tobacco use among youth are variable with sole e-cigarette use being the most common pattern of use. Additionally, there was a higher prevalence of substance misuse among youth who reported dual use and poly use than those who reported nonuse or sole use of e-cigarettes.

Similar to recent reports, we found that although sole use of e-cigarettes was the most common pattern of tobacco use among youth, the use of multiple tobacco products was not uncommon. (Park-Lee et al., 2022, Jebai et al., 2022) Evidence from the 2022 National Youth Tobacco survey showed that about 5% of high school students in the US reported using two or more tobacco products in the past 30 days. (Park-Lee et al., 2022) In another study, Jebai et al. showed that there was a significant increase in the prevalence of dual use of e-cigarettes and cigarettes as well as poly tobacco use among US youth between 2011 and 2020. (Jebai et al., 2022) This is a concerning pattern of tobacco use among youth since the effects of multiple tobacco product use include greater exposure to nicotine and an increased likelihood of addiction. (Gomez et al., 2020) Furthermore, the use of multiple nicotine-containing products during adolescents is concerning as the effects of nicotine exposure on developing brain function and behavior can be long-lasting due to interference with the brain's reward network. (Yuan et al., 2015, Vanyukov et al., 2012, Goriounova and Mansvelder, 2012a) There have also been reports of the increased risk of impulsivity, irritability, and anxiety among adolescents who report the use of multiple tobacco products. (Gomez et al., 2020, Miller and Hurd, 2017).

In addition to the health effects that are associated with multiple tobacco product use, our findings suggest that such patterns of tobacco use are associated with other high-risk substance use behaviors, which may further increase the health risks associated with tobacco use. In a study assessing adolescent risk behavior and use of e-cigarettes and combustible cigarettes, participants who reported sole e-cigarette use were 3.7 times (PR: 3.49; 95% CI: 3.16–4.32) more likely to report marijuana use in the past 30-days, while dual users of e-cigarettes and combustible cigarettes were 5.2 times (PR: 5.22; 95% CI: 4.42–6.18) more likely to report such high-risk behavior compared to nonusers. (Demissie et al., 2017) The aforementioned study also showed that dual use was also significantly associated with high-risk sexual behaviors such as having four or more lifetime sexual patterns among high school students. We extended these findings to examine the association of the patterns of e-cigarette use, including poly use, and a broad range of substances of abuse. Additionally, we examined if dual and poly users were different from sole users. We found that participants who reported dual or poly use were significantly more likely to engage in substance misuse than participants who reported sole e-cigarette use.

The coexistence of tobacco use and substance misuse, particularly among youth who use multiple tobacco products, may be explained by the gateway hypothesis or the common liability theory. The gateway hypothesis states that legal substances which include nicotine and alcohol may precede the use of illicit substances such as methamphetamine and cocaine. (Lozano et al., 2021) Thus, youth who use tobacco products may subsequently misuse other substances. However, due to the cross-sectional nature of our study, we cannot determine the directionality of the observed associations. For instance, while studies have shown that tobacco use can lead to initiation of alcohol consumption, the reverse is also true. (Lynskey et al., 1998) Therefore, preventing alcohol misuse among youth may also help curb tobacco use initiation. The common liability theory might also explain the association between tobacco use and substance misuse in adolescence. (Goriounova and Mansvelder, 2012a) During adolescence, the growing brain undergoes structural and functional changes that predispose adolescents to risk taking behaviors such as the use of tobacco and illicit substances. (Yuan et al., 2015) The observed clustering between multiple tobacco product use and substance misuse may thus be explained by their shared risk factor such as rejection of social norms, peer influence, and emotional and behavioral problems. (Demissie et al., 2017, Goriounova and Mansvelder, 2012a, Ozer et al., 2011).

Our findings highlight the high prevalence of dual and poly tobacco use among youth and the clustering of such patterns of tobacco use with high-risk substance use behaviors. The high prevalence of tobacco use among this age group emphasizes the need for stricter enforcement of policies that restrict youth access to tobacco products such as the Tobacco-21 legislation. Additionally, policies such as the e-cigarette flavor ban, which may reduce the appeal of e-cigarette use among youth, must be strictly enforced. Our findings also highlight the importance of comprehensive approaches to addressing youth tobacco use that include screening for high-risk substance use and counseling youth against these behaviors. Since e-cigarette use, particularly, when used with other tobacco products clusters with high-risk substance misuse, it can serve as a marker for identifying youth who may be misusing substances of abuse. Stricter enforcement of policies that restrict youth access to tobacco products and illicit substances are needed. Additionally, healthcare providers have a role to play in curbing youth tobacco and high-risk substance use. A prior study showed that brief counsel by healthcare providers can mitigate adolescent risk behaviors. (Boakye et al., 2023) Despite this evidence, the rate of tobacco screening among youth in the US by healthcare providers has been reported to be low.yyy³² To tackle tobacco use and substance misuse among youth, concerted efforts that include policies to restrict access, education and counseling on the health effects, as well as availability of evidence-based age-appropriate cessation interventions are needed.